The present invention relates to engine knock control systems in which an operating parameter such as the ignition timing is varied during dynamic operation i.e. acceleration, to prevent acceleration knocking.
At high cooling water and/or intake temperatures, audible acceleration knocking can occur in internal combustion engines if the load is increased very quickly, i.e. during dynamic engine operation. Knocking can be eliminated by retarding engine ignition. Therefore it has been proposed to temporarily retard engine ignition during dynamic engine operation to prevent the occurrence of acceleration knocking. In conventional knock-control systems if dynamic engine operation is detected the ignition is retarded by a fixed amount. However, retarding ignition has an adverse affect on engine response (gas emission) and therefore it is desirable to retard ignition as little as possible. The known systems for preventing acceleration knocking retard the ignition each time dynamic engine operation occurs, regardless of the ambient conditions. Thus, there may be instances when the ignition is retarded unnecessarily or more than is necessary.